Differences between disc ceramic and blue plastic caps?

[Doug Person]

I'm went looking for a 47pf cap for C73.  Naturally, (probably because
I'm an old-timer, ya know - kits from Knight-Kit, Johnson, WRL, Ameco,
not to mention the Benton Harbor stuff) I was looking for a disc ceramic
cap marked 47 with a black mark on the top.  Not finding any, I looked
through the parts list for the rf board where it indicated in might also
be marked 470 and be one of those little blue plastic caps. Just so I'm
sure before I solder these puppies in, C73, C20, C24, and C203 are OK as
little blue plastic caps marked 470, correct?

Tnx & 73,

Doug -- KØDXV
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[Don Wilhelm-3]

Doug,

Component markings have changed a lot over the years.  I would suggest that
you refer to the information in the ARRL Handbook on component markings for
an update on the various markings that are in current (and older) use.

Yes, a capacitor marked '470' is a 47 pf capacitor.  The little blue (or
yellow) ones will do just fine.  The old disc ceramics with the black mark
on the top are NPO type, which has the same thermal characteristics as the
'C0G' type.

It is not good practice to try to identify a component by its color - that
could change at the whim of the manufacturer, learning the current markings
for components is the only way I know to be certain about the designations.

73,
Don W3FPR

> -----Original Message-----
>
> I'm went looking for a 47pf cap for C73.  Naturally, (probably because
> I'm an old-timer, ya know - kits from Knight-Kit, Johnson, WRL, Ameco,
> not to mention the Benton Harbor stuff) I was looking for a disc ceramic
> cap marked 47 with a black mark on the top.  Not finding any, I looked
> through the parts list for the rf board where it indicated in might also
> be marked 470 and be one of those little blue plastic caps. Just so I'm
> sure before I solder these puppies in, C73, C20, C24, and C203 are OK as
> little blue plastic caps marked 470, correct?
>

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[Doug Person]

I understood the markings.  I just had misgivings about the equivalence
of the plastic blue caps and the disc ceramic NPO types that I am more
familiar with.  I do find the near microscopic print on these little
caps to be quite a challenge - even with a large magnifying glass.  I
can hardly imagine what lies ahead with SMD's - which will surely
replace all these through-the-hole type components.  Presumably my new
SMD soldering station will include a microscope along with the robotic
articulated digits to manipulate the components.

73,
Doug -- KØDXV

Don Wilhelm wrote:

> Doug,
>
> Component markings have changed a lot over the years.  I would suggest that
> you refer to the information in the ARRL Handbook on component markings for
> an update on the various markings that are in current (and older) use.
>
> Yes, a capacitor marked '470' is a 47 pf capacitor.  The little blue (or
> yellow) ones will do just fine.  The old disc ceramics with the black mark
> on the top are NPO type, which has the same thermal characteristics as the
> 'C0G' type.
>
> It is not good practice to try to identify a component by its color - that
> could change at the whim of the manufacturer, learning the current markings
> for components is the only way I know to be certain about the designations.
>
> 73,
> Don W3FPR
>
>  
>> -----Original Message-----
>>
>> I'm went looking for a 47pf cap for C73.  Naturally, (probably because
>> I'm an old-timer, ya know - kits from Knight-Kit, Johnson, WRL, Ameco,
>> not to mention the Benton Harbor stuff) I was looking for a disc ceramic
>> cap marked 47 with a black mark on the top.  Not finding any, I looked
>> through the parts list for the rf board where it indicated in might also
>> be marked 470 and be one of those little blue plastic caps. Just so I'm
>> sure before I solder these puppies in, C73, C20, C24, and C203 are OK as
>> little blue plastic caps marked 470, correct?
>>
>>    
>
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> You must be a subscriber to post to the list.
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>
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>
>
>  

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